The revelation came after a lawyer representing Cohen was ordered by a federal judge to release the identity of Cohen's third client during a hearing on Monday in New York. The hearing was sparked by Cohen's request to allow his team or a court-appointed attorney to review seized documents and determine whether the seizure will violate attorney-client privilege.
The documents Cohen is seeking to review were obtained by the FBI last week when the agency raided the attorney's home and office.
Prior to the Hannity news, it was also revealed that Cohen helped to negotiate a $1.6 million payment to a former Playboy model who alleged that she'd been impregnated by Elliott Broidy, the deputy finance chairman of the Republican National Committee.
Though it's currently unclear what work Cohen did for Hannity, netizens have taken to Twitter to speculate on the matter.